Could be anything. Could be a shift in hormones. Seemed like once per year, usually in spring or summer that I would have a late period. I'd take pregnancy test after pregnancy test and all negative. Then it would finally show up 7-8 days late.

Unless the women in your family went through menopause that early, chances are this is just a weird thing with your period. Could mean you're going to start showing some signs of perimenopause. A lot of women begin to have vague symptoms starting as much as 10 years before they actually go through menopause.